1. Technical Field
One of the sealless pumps is the permanent magnet canned motor pump, a device in which motor and pump are integrated as a complete unit, and an windings stator is isolated by corrosion-resistance containment shell, and an encapsulated inner rotor is directly in contact with the liquid to be transferred; another one is the magnetic pump driven by an induction motor, the sealless function is using a magnetic coupling to replace a mechanical seal; therefore, the sealless pump could meet the zero leakage requirement in industries, especially in high temperature, toxic, flammable and corrosive liquid transferred application. The invention focuses on a permanent magnet canned motor pump with a corrosion-protection housing, the corrosion-protection housing is comprised of an aluminum alloy motor casing, an aluminum alloy motor rear casing and a corrosion resistance plastic reinforced bracket, therefore, it will not damage the parts of the pump, even if there are some external chemical droplets dropping on the corrosion-protection housing, such as chemical liquid in the PCB manufacturing processes. The invention is also good for using in the filter tank system, the permanent magnet canned motor pump is installed under the filter tank, and is used to pressurize chemical liquid, so that while the filter is replaced, the problem of chemical liquid dropping on and corroding components of the motor of the pump is prevented. The plastic reinforced bracket is fixed on the pump casing of the pump, and thus keeping zero leakage on the sealing surface. Owing to the plastic reinforced bracket, the heat dissipating capacity of the outer surface of the aluminum alloy motor casing is limited. Accordingly, another object of the invention is providing a new heat dissipation mechanism to dissipate the heat generated by the motor at a sufficient rate.
2. Related Art
The permanent magnet canned pump is a device that integrates a motor and a pump, in tradition the permanent magnet canned pump has an outer shell comprised of an aluminum alloy motor casing with windings stator and an aluminum alloy motor rear casing, thereafter, called motor casing and motor rear casing respectively. Those components of the outer shell have cooling fins for providing sufficient heat dissipation capability, and with corrosion resistance material coating, (e.g. fluor-resin) for the operation in the environment in which corrosive drops may drop on. However, the performance of this solution for long term operation cannot resist corrosion well. Specifically, in the filter tank system used for filtering the chemical liquid, when the permanent magnet canned motor pump is installed under the tank used to pump chemical liquid, after a period of operation the cartridge filter inside the tank needed to take out and change the new, at this condition some chemical droplets may directly drop on the outer shell. And the capability of the outer shell for resisting the corrosive chemical liquid should be improved. One solution for improving the ability of the outer shell for resisting the corrosive liquid is that a motor guard made of corrosion-resistance plastic is placed on the permanent magnet canned motor pump. However, the motor guard is confined by the arrangement of the pipe lines, for example, the length of the motor guard is short and limited, and therefore, the metal parts exposed from the motor guard will suffer from the corrosion droplets of the chemical liquid.
The invention is focused on a corrosion-protection housing of the permanent magnet canned pump, in which the corrosion resistance plastic reinforced bracket protects an aluminum alloy motor casing, an aluminum alloy motor rear casing. In addition, the invention also provides a new heat dissipation mechanism for sufficiently dissipating heat that generated by the motor.
The followings are a conventional permanent magnet canned motor pump and a conventional magnetic drive pump, and none of them provide any effective solution to the chemical liquid droplet corrosion.
Taiwan Patent No. TWM369391 (hereinafter referred to as '391) which is issued in 2009 discloses an improved permanent magnet canned motor pump capable of operating at high temperature and resisting chemical corrosion.
This solution is focused on the shaft stiffness improvement of the pump, one of the features is a high stiffness cantilever stationary shaft of the motor, and the motor with a radial magnetic gap, too. Owing to the application, the encapsulation thickness in the '391 a 3 mm corrosion tolerance must be considered. That is the total width of the magnetic gap is at least 8 mm. The rigid composite stationary shaft is used to satisfy the working conditions are high temperature and high power requirements. The '391 shows that the structure of the permanent magnet canned motor pump of '391 is more concise than magnetic drive pump, since a magnetic coupler and an induction motor are replaced by a canned motor. As a result, the permanent magnet canned motor pump is more suitable for being installed in equipment which the size is limited. However, the '391 does not provide any solution to the problem of the corrosion caused by the dropped corrosive chemical liquid.
Another solution for the conventional filter tank system, please refer to FIG. 1, which is used for manufacturing printed circuit boards (PCB). The filter tank system 1 consists of a magnetic drive pump 12, a main frame 114 and a filter chamber 113. The magnetic drive pump 12 is assembled to the main frame 114, an inlet pipe 121 is connected to a tank of a PCB manufacture device, wherein the tank is used to contain chemical liquid; an outlet pipe 122 is connected to an inlet of the filter chamber 113 for outputting the pressured chemical liquid to the filter chamber 113. After passing through the filter, the chemical liquid flows back to the tank of the PCB manufacture device through the outlet 116. However, after a period of time, the filters in the filter chamber 113 need to be replaced by opening a top cover 115 of the filter chamber 115, and taking out the blockage filter, the chemical liquid droplets may drop out from the surface of the blockage filter. In order to prevent the chemical liquid from dropping onto the magnetic drive pump 12, a motor guard 123 is used. In practice, the main frame 114 has a limit in height, and the height of the outlet 116 must be matched up to the height of an inlet pipe of the tank of the PCB manufacture device. As a result, the motor guard 123 can not completely cover all metal components of the magnetic drive pump 12, for example, the bracket 124 in FIG. 1 is made of cast iron, and the motor guard 123 interferes with the tank exit 116 in height. Therefore, chemical liquid may drop onto and then corrode the bracket.
In view of the above, it is learned that the permanent magnet canned motor pump with the size of inlet and outlet of the pump meets a standard, it will have shorten the longitudinal length than the magnetic pump, and with this feature is easier installed inside the manufacture device. Besides, the area onto which chemical liquid may drop is reduced as well. However, demand for preventing the corrosion caused by the chemical liquid remains because the problem of the dropping chemical liquid can only be improved but can not be rooted out, furthermore, operator's oversight which causes the chemical liquid to drop out is unpredictable. Accordingly, the inventors recognize following problems needed to be overcome.
Problem 1: the heat dissipation of the motor.
Although the reinforced bracket made of corrosion resistance plastic can prevent the problem of the corrosion caused by the chemical liquid, the reinforced bracket also causes difficulties in arranging the cooling fins of the outer shell. Accordingly, a new heat dissipation mechanism for the motor is needed. The permanent magnet motor featuring in the high efficiency, which is higher than IE3 efficiency class of IEC60034-30 standard, can bring about dramatic reduction in the loading of heat dissipation, but the problem still remains.
Problem 2: the permeation of the chemical liquid.
The aluminum alloy motor casing of the '391 is connected to the pump casing and presses against the flange of the containment shell for preventing the leakage of the chemical liquid. However, the chemical liquid drops on the motor casing may permeate through the thread of the screw bolt into the tapped hole of the front flange of the motor casing. After that, the chemical liquid in the tapped hole may corrode and penetrate the aluminum alloy motor casing, and then the windings stator may be corroded.
The improvement of the invention can prevent middle-size and small-size permanent magnet canned motor pumps from the problem of corrosion of the dropping chemical liquid with reasonable cost. And the problem of the heat dissipation is overcome as well due to the improvement. As a result, the permanent magnet canned motor pump of the invention is more suitable for being assembled in manufacture device with confined interior space.